In the case of very popular factions, such as the Outcasts and Corsairs, they already have several close-to-canon factions each, so I expect it may actually be easier to get a splinter group OK'd than it would be to get a more vanilla group. That's assuming that the concept and RP for the splinter group is good, no powerplay shiplist or ZoI, etc. And it would still likely get flamed a bit for being YANHF (Yet Another New Hispania Faction), but in good hands I think it might eventually get approved.
Some examples of splinter groups, just off the top of my head:
Radical Outcast religious group, worships nomads as the Chosen of the Gods (Dom K'Vash).
Radical anti-nomad group of Outcasts, tries to purge the whole 'nomads as great spirits' belief from their society.
Order cell dedicated to foiling nomad plots outside the Omicrons (where the rest of the Order have things covered). Order ZoI is already pretty much anywhere, technically. Works from the shadows, avoids conflict with anyone not trafficking in nomad materials, infested, etc.
Junker assassins, they fly tagless (player faction tagless, Junker IFF and ID), do their Junker thing, but keep track of bounties and hunt people down in packs, all secret like. Ship names are changed often, to protect the guilty, and all communications/collections are passed through a single contact (unique forum account). This idea actually sounds pretty darn cool...
Gaians who've taken their environmental initiative out of Bretonia, to hit the despoilers wherever they may be. Gaian tag, generic pirate ID. Probably not very closely allied to the Corsairs or anyone else.
